What's the difference between spaghetti sauce and ...

Marinara sauce is a sort of all-purpose cooked tomato sauce that can be used in a variety of dishes.  It does not typically contain meat; the addition of meat would make it a "bolognese" sauce.  I suppose the term "spaghetti sauce" could be used to designate any tomato-based sauce used for pasta, including those containing meat.  Hope that helps. 

Marinara - using White Wine in the cooking process and adding Seafood. While using the Basic pasta sauce recipe. Marinara Meaning "Marine"(From the Sea)

Spagetti sause is thinner than Marinara which is used with,chunky tomatoes and is cooked for a shorter time period than sauce.

I've done some research for you to get the official answer.  According to what I found, all maranara sauce is spaghetti sauce but not spaghetti sauce is not maranara sauce.  If you put either on spaghetti it's spaghetti sauce.  If you put it on pasta or meat it's maranara sauce.  What I feel from buying both already made is that spaghetti sauce is thicker and has less chunks.  But I have used both on spaghetti and other pasta.  When I want a thick sauce I use spaghetti.  When I want a thinner sauce I use maranara.  Hope this helped.